Back brace



FIG. 1 is a lower perspective view of a back brace, showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a left side elevational view thereof.

The broken lines shown herein are for illustrative purposes only and form no part of the claimed design. The right side elevation view of the back brace in FIG. 1 is a mirror image of the left side elevation view shown in FIG. 5. 

The ornamental design for a back brace, as shown and described. 